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Technology Description
Desktop system
HMD system
Projection system
A Generic VR System?

As technology advances, it is difficult to talk about a singular 'VR system' as modern systems are made up of a number of different components depending on the user requirements for specific VR applications.

A typical VR system consists of at least the following components:

Computer - the most popular graphics computer for VR systems is still an SGI Onyx, but rapidly growing capabilities of consumer graphics hardware in the PC segment, now allow the rendering of complex, texture-rich virtual worlds on this comparatively cost effective hardware platform in real-time.

Visual display - different visual displays are available for VR systems, typical examples include a standard CRT monitor, an HMD, a projection screen or a ´reality theatre´ or CAVE.

Input device(s) - are necessary in order to navigate and interact in the VE. There is a wide range of devices available and those selected will be affected by the display device that has been chosen for the system.
For example, if an HMD is used, an input device would need to compliment it so that the participant would not be required to look at it to understand its operation (e.g. a detailed keyboard). Conversely, a desktop system would tend not to be used with a tracked input device as there is limited space for movement available.

Software - sophisticated software is used to run VEs in real-time. Software is also used for tracking or force feedback (where this is used). The VE software must co-ordinate the inputs from the participant's movements and interactions and update the VE accordingly using real-time rendering and displaying of the VE.

Many forms of VR system exist. Some typical VE systems that are commonly used are described below:
Desktop system

A typical desktop system uses a standard CRT monitor (or LCD laptop screen) as the display device. The participant is not enveloped in the VE but has a 'window' into the VE. Interactivity and navigation are achieved either via advanced PC input devices such as the Spacemouse or multi-axis joysticks. Alternatively the VE interface can be designed to incorporate icons that allow the

desktop in VR-systems

participant to navigate or interact in the VE using standard PC input devices (mouse, standard joystick or keyboard etc). Specialised software packages allow VEs to be created and run on desktop PCs.

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HMD System

A typical Head Mounted Display (HMD) consists of a helmet with two small displays (CRT or LCD) and an adjustable lens system. HMDs are the first projection systems which have been developed specifically for viewing VEs.

They can produce stereoscopic viewing by presenting separate overlapping images to each eye. They are widely used for military and medical applications. They vary in cost, and some devices can be desirable and affordable for home users as display devices for 3D games. Interaction and navigation are achieved through specialised input devices, for example 3D mice, wands or data gloves.

The HMD and the input devices are tracked in real-time using an electromagnetic tracking system which is transformed by the computer to update the participant's position within the VE. HMD systems are usually used by single participants, however it is sometimes possible for multiple participants to inhabit the same virtual environment.

HMD System


HMD System
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Projection system (power wall, holobench, L-shaped systems, etc)

In a typical projection system, the VE is projected onto a free-standing or wall-mounted projection screen via conventional three-tube video projectors.

The VE can be viewed by a number of participants at any one time, depending on the size of the projection screen and the space available.
The VE is usually manipulated and interacted with by one participant with the remaining individuals as passive observers.

Navigation and interaction typically takes place using standard PC input devices, however more sophisticated devices can be used. There are many types of systems that come under the generic heading of projection systems, these are generally classified according to the display type.

Projection system


Projection system
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CAVE & Re-configurable System

2 - 6 walls (fabric or plastics) form a projection area or room (CAVE). CAVE systems consist of two or more walls and a walkable floor all with rear projection. Compared with a power wall the floor and additional walls extend the interaction volume and therefore the sense of immersion.

In particular a 6-sided CAVE requires wireless tracking, interaction and sound devices. In contrast to dome-like or

Reconfigurable CAVE

curved screen systems, the flat walls guarantee a defined undisturbed projection. Re-configurable systems combine the advantages of different projection systems. They can be more or less easily adjusted to meet application specific requirements.

A CAVE (courtesty of FhG-IAO)
6 Sided CAVE
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